1. Field of the Invention
This invention relates generally to dentistry and in particular to a method and an apparatus for placing, compacting and shaping a light-activated dental restorative material in a cavity preparation or between adjacent teeth and for polymerizing said restorative material in said cavity preparation or between said teeth to produce a restoration.
2. Description of the Prior Art
Increasingly, dentists have been using light-curable dental composites as restorative materials. The composite is generally applied to the tooth using a conventional placement instrument or a plastic filling instrument. The composite material is compacted using a condenser and contoured to the shape of the cavity preparation using a carver or bur. When light is shined on the composite for a predetermined time, the composite is polymerized and bonds to the tooth.
Typically, light is transmitted from a light source by a fiber optic cable and a hand-held light wand. The light intensity on the surface of the restoration depends on the light source and the distance of the light source from the restoration. To insure depth of cure, the light should not be held too far away from the restoration. This is difficult to assess when using a hand-held light wand. If the light wand is held too close to the restoration, only a small area is illuminated, leaving marginal areas inadequately cured.
A transparent, cure-through, double-ended instrument is disclosed in Parkell Products Update catalog, Winter 1987/88 issue. The Parkell instrument is a double ended instrument made of light conducting polycarbonate and is autoclavable or cold sterilizable. The working ends of the instrument are polished, whereas the handle comprising the middle portion of the instrument is matted or abraded. In using this double-ended instrument, curing light is applied and transmitted from a direction perpendicular to the handle. As is well known, a polished surface reflects light internally whereas a matted surface diffracts or emits light. Thus, a significant amount of light is emitted from the matted surface of the handle of the Parkell instrument and lost before it can be transmitted to the working ends. The instrument is inefficient and as a practical matter requires increased curing light exposure time to insure depth of cure.
U.S. Pat. No. 4,673,353 to Nevin discloses an apparatus for exposing a light-curable dental composition to a curing light to harden the composition while the composition is applied to teeth so that the exposure of a dentist's eyes to such light is minimized. Nevin's apparatus has an opaque receptacle which is open at its top and bottom; dental composition is picked up and discharged through the bottom opening. An elongated plunger having a clear plastic core and an opaque surface coating has a working end which extends through the top opening of the receptacle and an opposite end connected to a source of curing light. In Nevin's invention, the dental composition is exposed to curing light transmitted from the working end of the plunger while the filling material is held within the receptacle and while the working end of the plunger is forcing the filling material out of the receptacle onto a tooth. Nevin further discloses modifying the apparatus by in part eliminating the opaque receptacle and shaping the working end of the plunger so that the plunger can be used as a tool for shaping light curable composition. However, to protect the user's eyes, Nevin retains the opaque coating on the side surfaces of the plunger between its ends. This limits the usefulness of the apparatus as curing light is emitted only from the tip of the working end of the apparatus and not from its sides.
U.S. Pat. No. 4,666,406 to Kanca, III, discloses an attachment device for a fiber optic wand comprising a rod shaped or needle like fiber optic tip or end cap. In practice, the fiber optic tip is placed in close proximity to composite resin in a cavity preparation and the light source is activated so as to expose the composite resin to a substantially proximate curing light source. The device cannot be used to place, compact and shape dental restorative material in a cavity preparation; neither can it be held against the shaped and compacted restorative material to maintain the desired shape of the restoration while curing light is delivered to the restorative material.